


Questionable Decision - Preferential Outcome

by QueenEchidna



Series: Everything's made up and the boundaries don't matter [1]
Category: Undertale (Video Game)
Genre: (slight) - Freeform, Bottom Papyrus (Undertale), Come Inflation, Creampie, Dom Sans (Undertale), Dom/sub, Ecto-Genitalia (Undertale), Ecto-Penis (Undertale), Ecto-Tongue (Undertale), First Time, Fontcest, I won't lie this is a nasty fic but it's most of my favorite things all in one, M/M, Mutual Pining, Penetrative Sex, Pining, Praise Kink, Sibling Incest, Slight Dubious Consent At The Beginning, So don't read this if you're not into sticky incest skeleton sex, Sub Papyrus (Undertale), Top Sans (Undertale), Vocal Papyrus, classic fontcest
Language: English
Status: Completed
Published: 2018-11-12
Updated: 2018-11-12
Packaged: 2019-08-22 12:18:30
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 8,133
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/16597781
Author URL: https://archiveofourown.org/users/QueenEchidna/pseuds/QueenEchidna
Summary: "I would hope you were my biggest fan Sans." Papyrus said in almost a mumble, seemingly hesitant to say it, his face was dusted with color and he smiled sheepishly at his brother. Again, Sans held his breath, his face lighting up a rich blue, the magic between his legs stirred dangerously--.-.-.-.-.-This fic was a long winded excuse to write some classic Fontcest with some of my fav kind of smut. There's lots of nasty stuff, not particularly kinky, but just be warned I had no chill with this fic.





	Questionable Decision - Preferential Outcome

**Author's Note:**

> The setup of Papyrus walking in on Sans is pretty inspired/taken from trousledbones amazing comic (which I can't find anymore for some reason so they may have removed it, which would honestly be a tragedy) 
> 
> This is a nasty fic and some aspects may not be for everyone, so please check my tags before you dig in!  
> Otherwise I hope you enjoy and I'd love any comments and feedback!

"-and Undyne is finally going to let me do some puzzle practice with her! And good for her, I say: it will be a great exercise in sharpening her skill and mind simultaneously! Now I'm probably going to have to start her out with some Junior Jumble to really ease her into it, I know my puzzle-solving genius doesn't come quite so naturally to other monsters!" Papyrus had been a non-stop motor mouth since they left the house that morning, though even after a full day of errands and scheduled arrangements with friends and businesses alike- Sans still happily, albeit passively, listened and noted every word his brother rambled on about. 

 

Reaching the front door of their home, Sans somehow managed to get the door unlocked and opened even with both his arms full of groceries. The lights were still on? He knew he turned them off before they left. 

 

" **Ah hello darlings!** " 

 

Sans groaned without even having to peer beyond his grocery bags; he knew who it was and wasn't surprised a bit that said person had no problem making themselves at home here. 

 

Papyrus, in his excitement, dropped the few bags he was carrying, "Metta! Blook!" He ran to his friends to embrace them eagerly, allowing Mettaton to pick him up and twirl him around. Napstabot had his hands clasped together as he smiled in greetings. 

 

Sighing through his teeth as he struggled to get all the groceries into the kitchen, Sans glared at the pink mech so audaciously pawing at his brother; it was nothing new, of course, however not an instance went by which didn't infuriate Sans. The first time Mettaton decided to get so... _physical_ with Papyrus was right after that near-death experience on his TV special, and it was almost acceptable that the two would be happy to see each other after such a strenuous experience. After that, it seemed like none of the situations ever called for them to embrace, yet Mettaton didn't seem to mind snatching the younger skeleton up whenever they crossed paths. 

 

"How was your tour?" Papyrus wondered aloud, now greeting Blook with a much more chaste hug. 

 

Dramatically spinning on his heels, Mettaton whined, "Oh, magnificent as always," He slunk behind Napstablook and wrapped his arms around the shorter mech, who smiled shyly, "Everybody loves my little cousin, he's such a sensation you should come to a show sometime and really see him shine!" Mettaton shot an adoring gaze at Blook, before sweeping over to Papyrus. He slinked his arm around his waist and pulled him down to sit on the living room couch together, practically sitting the skeleton in his lap as he did so. 

 

From the kitchen, Sans' magic flared up in annoyance and he nearly crushed the carton of juice he was loading into the refrigerator. Although, much like every other minor (or in this case major) annoyance in his life, it was nothing new, and he had been forced to bear witness to yet more manhandling of his little brother many times preceding that. Papyrus himself insisted it was all innocent and meant nothing to him, and that Metta was just a "very touchy-feely" person, and Sans shouldn't be so protective. 

 

He took a deep breath to calm his anger. He wanted to believe Papyrus, and acknowledged that he was probably right, and Sans was just looking into it too deeply. Mettaton acts the same way towards just about everyone, whether it be on live TV, or in their living room; it was never especially different behavior from one person to the next. But nothing could ever stifle the jealously that welled up in Sans' chest whenever he or someone else would put hands on his brother. 

 

Sans stopped himself, trying to stay calm, trying in vain to remind himself that those feelings were perverse and should be maintained, especially considering the nature of most of them. He just... couldn't do that to Papyrus. 

 

Thoughts and feelings stirred in his body, ones he didn't care to think about or acknowledge: ghostly, accidental touches that sent shivers through his bones, big innocent eyes and an unknowingly adorable smile that brightened his days and made him feel nice; because if that precious monster loved him, then maybe he wasn't so bad. But those were all things he had pushed away long ago, now coming back and clouding his mind, angered and jealous whenever someone else got to get close with Papyrus while he held himself back. 

 

Again, he took a breath, cautiously drifting his gaze to the living room, where he others were enthusiastically sharing stories and jokes. His breath hitched when his gaze met Papyrus', although he succeeded in acting fairly normal by grinning and holding up a box of his brother's favorite cereal he had just grabbed out of the grocery bag. 

 

Papyrus smiled at him, big and cheery and beautiful, like the rest of him. His eyes glinted a faint orange glow in his mirth, and he gave his brother a big thumbs-up. Sans relaxed a bit, everything about his brother calmed him and made him feel happy, made him feel good... But it could not be helped. It was becoming increasingly difficult for him to hold back and keep his dirty secret in the dark, especially when night came and he was alone and weak to his imagination's guilty claws. Most nights he was subject to a barrage of lecherous scenes involving his brother, he could not stop them as they flashed behind his eyes, just as he could not stop the growing swell of magic below his belt as he watched them. His joints would glow as his arousal increased his spill of magic to his extremities, and his dick would jut out eager to be attended to. Every moment felt dirty but so, _so_ good. 

 

He hung on every falsified word spoken in his brother's voice, relished in the imaginary touches, very naïve and unsure, where he felt himself being carefully handled; the way Papyrus' voice would shake and struggle to get out words as Sans' expert hands wove their way through his bones and made him wiggle. Sans would drool at the sight of his brother's licentious behavior; his head thrown back as he called out his big brother's name, one hand tugging on himself and the other grasping at Sans' back. 

 

The number of times he had fooled himself with those fantasies was too high to count, and while he rather enjoyed his secret that remained an unspoken personal activity, he was beginning to confuse his fantasies with reality. Too often would he find himself almost groping and grabbing at his brother like it was no big deal, or worse yet, when he would return home late, and drunk, and practically fall into Papyrus' room. Though thankfully, every time he managed to catch himself, punishing his rampant lack of cognizance and moral with a freezing shower. 

 

When a time arose in which Sans may have finally been at-peace with his... _problem_ , accepting that as long as it was never acted upon it was not going to hurt anyone else- there was always something that succeeded in reminding him just how disgusting he was. It was often a passing comment from Papyrus, about how much he loved and trusted Sans; and then that familiar feeling of guilty heat would swirl in him and cement his self-hatred on the subject. That was his little brother, whom he had all but raised; what he felt was not normal, and he did not know how to explain it. Worse things could happen, and there were worse people to love but-… When Sans looked at Papyrus, having fun with Frisk, playing his games, cooking with Undyne- this all made Sans incredibly happy, he did not want to take away that wonder from his brother for something so shallow as his desire. 

 

It was hard, lord, was it hard for him to keep it all in; he could hardly believe how accidentally flirtatious Pap could be, how handsy he could get when they were snuggled up on the couch together, not knowing that him innocently tracing his brother's ribs through his shirt was driving Sans towards an edge he did not want to be nearing. 

 

And he was just so _adorable._ Always walking with a skip in his step no matter where he went, smiling at everyone, singing without knowing it when he set up his puzzles: Papyrus was cute, another mannerism that guiltily turned Sans on in his weaker moments. It was always little things he did throughout the day that drove Sans nuts, and he often found himself having to make excuses to leave for the day just so his guilt wouldn't drive him to nausea. Although the disappointed look on Pap's face when he left hardly seemed worth it most of the time. 

 

Sans forced himself back into reality as he felt that same feeling of bubbling magic begin to grow uncomfortably at his groin. He could feel the heat on his face and see his eye glowing bright blue in the reflection of the toaster sat on the counter. Knowing it would take a few minutes to calm down, Sans used the excess magic to teleport to the bathroom, shutting the door behind him. 

 

From his place on the couch, Papyrus faintly noticed his brother blip out of sight in a faint flash of blue. A frightened panic rose in his throat and he jumped up from between Mettaton and Napstabot, worried something was wrong, he excused himself and following the faint magical trail that pointed him down the hall. He was met with a closed door and heard slightly heavier breathing from the other side, "Sans are you alright?" He wondered. The breathing completely stopped for a moment before continuing at a steadier pace. 

 

Sans cautiously opened the bathroom door, just enough to stick his torso and head into view, he had to avert his eyes, as his brother's worried, flustered look was a little too much for him at the moment. He noted Papyrus had changed and was now wearing a light peach colored sweater with little embroidered white hearts scattered over it: he assumed it had been a gift from Mettaton as he always had something for Pap when he came to visit. 

 

"Yeah I'm okay bro." To be fair it was only half of a lie, since he was only about half as hard as he normally was. 

 

He could see it in his eyes that Papyrus did not accept that answer as truth, nor a convincing enough lie, however he was saved from having to force a formal conversation when Mettaton boisterously beckoned for the younger monster's return. Obligated by social construct, Papyrus gave a strained sort of smile, "Well alright, if you're sure. But let me know if you're getting sick or something." He said, reaching out to run gentle digits over his brother's cheek. 

 

Sans had to hide a gasp, "Will do bro." Again, Mettaton called for Papyrus to come back. "You should hurry: your biggest fan is waiting for you." He chuckled and dodged a playful slap from his brother. 

 

A look swept over Papyrus' face as he took a step back from the door; it was sort of timid but still cheery, "I would hope you were my biggest fan Sans." He said in almost a mumble, seemingly hesitant to say it, his face was dusted with color and he smiled sheepishly at his brother. Again, Sans held his breath, his face lighting up a rich blue, the magic between his legs stirred dangerously and he was grateful he had had the foresight enough not to expose more than his head and torso. 

 

He cleared his throat awkwardly once... twice... three times, rubbing the back off his neck and trying to mask the behavior as some kind of twitch, "Uh, y-yeah, of course I am Pap." He said sincerely, though his voice probably sounded shaken and cross. He took a deep breath, pushing thoughts and visions from his mind for just a moment in favor of being truthful and flattering his brother, "I'm the biggest fan of the best monster and soon-to-be Royal Guardsman in the entire Underground!" He waved his hand in the air, reveling in Papyrus' giddy laughter that followed. His baby brother smiled at him like he put the stars in the sky (or the rocks in the cave, in the case of the Underground), before he gave a little wave and retreated to the living room with their company. 

 

Finally alone, Sans sighed hard and flopped down on the side of the tub, running his hands over his face frustrated as he opted to ignore the growing problem in his pants. He was not about to jerk off in the bathroom while they had people over like some horny teenager. No, he would deal with his problem like an adult. 

 

He proceeded to teleport to his room and turn up his most obnoxious trap remix tape to drown out his guilt. 

 

-.-.-.- 

 

Papyrus stalked quietly to his brother's room. Mettaton and Napstablook left after a couple hours of revelry, and only then had he noticed his brother's complete absence from the whole affair. Of course, he was wrought with guilt over having accidentally excluded the person he cared for the most out of them all, and currently held a plate of spaghetti to make up for his negligence. 

 

However, upon reaching the door he began hearing a string of muffled sounds. Little whimpers, grunts, and what sounded like sobs met his ears, and a pang of guilt shot through Papyrus' heart. Tears welled in his eyes at the thought of his lack of attention forcing his normally much more emotionally resilient brother to break down crying in the emptiness of his room. _'He must have felt so lonely, with all of us having such a good time.'_ Papyrus thought, whipping away a stray tear from his cheek. 

 

There were a few moments of fear that gripped his chest and kept him still, the thought occurred to him that Sans may be too mad to even speak with him, too upset to appreciate the apology spaghetti, and then it would all be in vain and he would have to do it all over again. Not to mention, when Sans got upset like this, he was not as kind and patient with him as usual. Which would have been understandable, considering it was his fault Sans was left to fend for himself all day. A painful sadness tugged on his heart after he remembered they had planned a game night for just the two of them that night, and with Mettaton and Napstabot's unexpected arrival, Papyrus completely forgotten, accidentally forgoing the planned events. Sans must have been feeling so betrayed and hurt. _'I knew he wasn't feeling good and I left him alone, I ruined our plans, I messed up so badly! What kind of brother does that?'_

 

He decided enough was enough and that a proper apology was in order on his part, no matter how close he was to crying, he was going to puff out his chest and fix what he had done. His mind was already ablaze with ides for an apology game night! He could cook a whole dinner and put on a compilation of those idiotic videos he spends all day watching and serve it all up in their living room while they played a game! Without further hesitation, he opened to door, "Sans I am so sorry, I never meant to exclude you!" 

 

" **Papyrus wha-!** " Sans did not know how to react, as his little brother stopped in front of him, with a complete view of him sprawled out, glowing, sweating, with his hand frozen in place around his swelling member. They made eye contact, which was extremely awkward and only served to make things worse. Sans mustered the will to grab a blanket and cover himself. 

 

Papyrus' face flushed orange and he averted his gaze as soon as he realized what he had done; apparently those noises he heard were not Sans crying after all. He had been... well, he didn't have a word for it, but he knew what it was: Metta had talked about it before and when Papyrus went to Sans for a more conceivable explanation, he was quickly turned away. "Uh, s- sorry..." He exclaimed, his limbs shaking as he backed up. His shoulder hit the door frame and the shock of it caused him to drop the plate of pasta. The plate did not break thanks to the plush carpet, and he went to pick it up before the swelling in his chest forced him to abandon that and bolt outside the door. 

 

He pressed his back against the wall a few feet from Sans' door, his breath was coming in raged gasps, his heart was in his throat, heat and sweat began prickling along his brow as his face flushed a darker orange. Even more heat travelled through his body, making every extremity feel warm and pleasantly albeit inexplicably numb; the hot magic his body was beginning to excrete started to pool in his lap. 

 

And it all felt so _good._

 

Perhaps the full understanding was lost on him, and he did not understand why or what was happening to him, but what he did know was seeing Sans like that made his insides stir and his magic surge and build up uncomfortable and hot all over him. The little moans he heard still rang in his ears, the brief sight of Sans' tongue lolled out to the side with a huge grin on his face made his heart skip a few beats. 

 

Moments later, Sans came running from his room still pulling his pants up; he was sweaty and out of breath, although he was more worried about what he had exposed his brother to more so than his own discomfort. "Pap-!" He turned, glaring at the floor in his frustration. "Buddy I'm sorry, I should have locked it!" When he finally shifted his gaze to look apologetically at his brother his chest clenched almost painfully. Against the wall Papyrus was flush and his chest heaved with his labored breathing. One hand was braced against the wall while the other hovered over his agape mouth to attempt to hide the sight of him drooling around his protruding tongue. 

 

He was making tiny, _delicious_ moans as he stood there practically falling apart in frustration. Sans had to use all of his willpower to keep from pouncing the younger monster right then, because the sight of his brother writhing in arousal against the wall, face stricken with an innocent gaze, was just about the biggest turn-on Sans had ever seen. _'Disgusting...'_ He cursed inwardly, unable to counter the lewd thoughts in his mind. His brother was experiencing something strange and uncomfortable to him, it was not right. 

 

" _S-S-Saaanss...!_ " Papyrus moaned long and loud, turning his head to look at his brother with lidded, confused eyes. 

 

"Oh, oh my god...!" Sans bit his lip, frozen on the spot by the sound of his voice crying out like that, the added benefit of his name being moaned like that was nearly enough to push his to the edge. 

 

The taller monster wiggled, gasping when his rear brushed against the wall, "What's h-happen...ing? My... my magic is- _mhh_ \- is acting up!" Sans watched as Papyrus was nearly torn apart with every little movement, how every shift or fidget sent waves of heat through his body and made his knees weak. 

 

Papyrus spared glances at his older brother, who seemed frozen on the spot, and his body did not seem to know how to react as the attention made his chest swirl, but the embarrassment of it made tears prickle in his eyes. 

 

"I, uh-" Sans was at a loss for words, and there was no way to pull himself back from the mindset he was in. It was like every one of his fantasies rolled into one, and though he knew it was wrong, he wished he knew a way to make it happen, he wished he could take what he wanted but leave his brother's innocence intact. "It's normal, Pap, don't panic. Uhm-" He fumbled around, hating how his tongue heeded his articulation; he reached up to rub a shaky hand along the back of his neck, all sensibility gone and replaced with nothing but raw need, although he was trying everything in his power to not act upon it. 

 

Based on his confused and flustered state, it was clear Papyrus had little to no idea as to what was happening to him; taking advantage of that would be despicable. But it was so tempting. And clearly his brother needed help somehow. 

 

He steeled himself, wiping away the sweat on his forehead, and using the strength he cared not to utilize to quell his magic to some semblance of calm rather than the raging inferno it had become. It was going to take more than a sticky libido and a perverted display to make him loose respect for his brother; fantasizing was one thing but acting on it was something else. Pap's body was reacting to something, and as his brother and protectorate, Sans accepted that he could not think so selfishly, and that at that moment, Papyrus needed him to be strong and turn a blind eye to his physical desires- 

 

"Big brother..." Those words, squeaked out in a needy whimper successfully undid what Sans was building up to and his arousal flare back up with a vengeance. "What do I do?" Papyrus asked quietly, his voice shaken and sounding scared. 

 

A perverse thought flashed through Sans' mind, but he quickly shook it away. Hauling his still frozen body forward, Sans carefully ushered him away from the wall and into his room, licking his lips as every time he made even the slightest contact Papyrus would roll his head and moan. They sat down on the bed. "Just t-take a deep breath and don't think about it too hard." Every word coming out of his mouth was pointless ramble, he didn’t know what he was saying or what he should say for he was far busier keeping himself from kneeling his brother down and blowing a load on that pretty face. 

 

He truly surprised himself with the dirty things his mind was wandering to. 

 

His brother's big, sad eyes looked at him in confused thanks, "I feel so...so h-hot." Small tears speckled his lower lids, which Sans reveled in wiping away; cupping his hand over Papyrus' flush, trembling cheek and tenderly rubbing his thumb beneath his eyes. He wanted to kiss him. 

 

The heat, which had failed to dissipate since his brother barged in, resurged and made him tense up again. It did little to help when Papyrus smiled in response to his small gesture of compassion, settling down against his chest and nuzzling into the crook of his neck while occasionally moaning softly as his growing heat was becoming too much to bear. Sans had to fight to keep his breathing somewhat normal, which was nearly impossible since every time Papyrus breathed out it sent a gentle wave of warm air to caress his vertebrate there and drove him wild. 

 

_'Shit- shit- shit- fuck- fuck- ffffuck-!'_ Sans groaned internally as his magic began to boil over as he lost control. His ribcage was alight beneath his shirt where his magic was pooling, and the bulge beneath his shorts grew and ached to be touched; he tried to temporarily aid his suffering by gently palming himself through the fabric. It did nothing to help as it almost made him cry out. _'What can I do? Oh fuck oh fu-uck, I can't take this I can't control it-!_

 

"What's wrong b-brother?" Papyrus asked, full of curiosity and worry. Sans flinched, looking away and trying to hide the trembling of his frame. It was embarrassing: he was reduced to a horny, mess almost exclusively motivated by his dick, because of his baby brother. He felt bile rise in his throat as the term both disgusted and aroused him, he hated himself for how he felt. 

 

He coughed dryly, "Oh, uh, nothing, just tired." He hoped a blatant lie would get the point across that the other should leave. Unfortunately, although he is adept at many things, picking up on social queues is not one of them and his brother sat unmoving, pressing further against him, moving his hands over Sans' body as he both checked for anything that might be amiss, and satisfied the growing desire to be touching his brother. 

 

"You're... you're hot t-t-too." Papyrus whispered, looking and sounding equally scared. His hand settled on the center of his chest and he felt San's rapid breathing. His blush deepened and he gasped silently before asking, "I-I could help you. I-If you want..." 

 

Those words began to undo Sans, though his guilt did not miss the chance to berate him for taking such vulgar and lewd pleasure from hearing those words come out of his brother. His brother's sweet, sincere face only served to drive him crazy; he laid a shaking hand on his cheek, gasping as Papyrus nuzzled into it and kissed his palm. 

 

With his brother's body so close to his in such a state of vulnerability, it didn't take much for him to lose himself to his needs, his vision clouded over and suddenly every idea seemed like a good one. "P-Papyrus I – fffuck-!" He dropped himself backwards to lay flat on his bed, dragging the other down with him. Papyrus made a strangled sound of confusion and concern as he was pulled down and held in place by a pair of searing hot hands around his wrists. He looked around, dazed and unclear as to exactly what happened before his gaze settled on his brother below him. 

 

The sight that met him made his body heat up uncomfortably. Sans was hardly there; in his place was a hungry, lust-driven beast. He could see it in his normally kind, sleepy eyes, that there was another, more ravenous turmoil spurring him on, his mouth watered noticeably and his hands grabbed hungrily at whatever part of Papyrus he could reach. Within moments he was grinding himself up against Papyrus, eliciting a strangled sort of sound from the younger skeleton. He couldn't find it in him to care about the emotions behind the noise, all he cared about was finally getting the stimulant he craved. 

 

"W-What's happening Sans?" The youngest croaked nervously, feeling his body reacting with heat and want but not quite understanding why or what to do with it. 

 

Sans reached out, easily removing Papyrus' pants by sliding the other off his lap to pull them off, and although confused, it did not occur to Papyrus to protest as he could feel how good it was making him feel although he did not quite understand. Whatever Sans was doing was both relieving and building up the heat that was plaguing his frame; he was being driven wild by the hot body against his, and the guttural, possessive sounds that came from his brother's mouth made him want so much more. 

 

Papyrus was knowing and experienced with his own body at least, so it already knew how to form his dick, which stood glowing a light orange in the relative darkness of the room. Sans sat up and got close, wrapping one arm around Papyrus' waist, while his free hand went between his legs, caressing the stiff member that begged to be touched. The slightest contact made Papyrus' body jolt as he cried out, latching onto his brother's head and shoulders, he began moaning out lewd pleads, quite sure this was much better than doing it by himself. His body squirmed and bucked as Sans moved up and down at varying speeds, thumbing the tip, applying excess pressure occasionally. Every move Sans made seemed purposefully and skilled, and he jealously wondered if he had done this with anyone else. 

 

Time stood still for Sans, he was lost in his ministrations, completely at the mercy of his brother's whimpers and cries, spurred on by the feeling of a hot body flush against his and demanding attention from solely him. The guilt was still there, sitting in the back of his mind like a forgotten responsibility, but he was less inclined to recall it as Papyrus moaned out a long string of pleads, ending in whispering Sans' name right into his ear. 

 

An instant later Papyrus was laid back on the bed, now fully exposed. Still squirming and whining from the lack of contact. 

 

For a moment, Sans stopped, his hands slowly raking down his brother's sides, eyeing up every exposed and flushed inch of his body. _'Stop it, stop it, stop it! I'm such a piece of s-shit, I'm about to- oh my god to my brother-!'_ Somewhere in his lust-clouded mind he knew this was wrong, it was so immeasurably wrong even if Pap had offered; Papyrus probably didn't even know what was happening, why was it so hard to just stop? 

 

He could not take his eyes off the beautiful sight of Papyrus, completely disheveled and panting while gasps and moans erupted in a glorious harmony as Sans touched him in ways he'd never felt before. And Sans was more than happy to indulge him, touching, kissing, sloppily lapping at every sensitive spot he found to make his baby brother cry out for more. And he wanted to give him so much more. He had every intention of giving him something that would make him scream, he wanted to hear Papyrus calling out his name as he was defiled within an inch of his life, completely at the mercy of his big brother's cock. He wanted him to beg for it every night, he wanted to ravage Papyrus every night and do something new to him every time- 

 

The guilt and hesitation were still there. Even though moans, pleas, and cries of ecstasy are typically a sign of willingness, he was terrified he was about to do something to his baby brother that could never be reversed and that would ruin him. He didn't want to lose his brother's love and respect over something as trivial as sex, that could not happen. "You still want to h-help me?" Sans' voice shook; it was more of a warning, to see if the younger monster had any clue what he was getting himself into. His mind was so loud with differing arguments, all while he was stroking his member while caressing the sensitive joints in between his brother's bones making the younger monster shiver. 

 

"Sans?" A quiet voice silenced his mind, and he gazed down at his brother; his sinfully, innocent, beautiful brother, whom he wanted no one to touch besides him. "I want you... h-however this works I... I trust you to use m-me as necessary." His face was flushed a dark orange and his right eye glowed as his magic spilled over; he looked confused at his own arousal, and those trusting eyes looked to their big brother for reassurance and guidance. 

 

Sans reached out and scooped his brother in his arms, kissing him, and rubbing the same comforting circles on his back as he had just a few minutes ago. When he pulled away, Papyrus stared at him, mouth open and breathing heavy with his eyes half-lidded. He rested the younger monster down onto the bed and crawled between his legs, taking his dick in hand once more. "Don't worry Pap," He murmured huskily, pulling his hips up to line up with his brother, "Your big brother will take care of you." He punctuated the sentence by nipping at Papyrus' neck as he broke the still moment by shoving himself into Papyrus. The magic gathered between Papyrus' tail and pubic bones made a wonderful sheath for Sans to fill with his member. 

 

" **S-SSANS OH MY- S-S-SAAH- AH-!** " Papyrus screamed at the foreign feeling that began stretching him out painfully, he blindly reached out and wrapped his arms around Sans' neck as his brother began to thrust into him hard and fast. He didn't understand; the pleasant heat was there still, but this was nothing like it felt before; now the heat was mostly from pain and he wasn't sure how he felt about it. 

Page Break

 

While he continued his ministrations, Sans lifted his brother's legs up onto his shoulders as to get a better angle, easily moving himself in and out, reveling in the warm heat his brother gave him, how tight he was, and the glorious sounds he was making. The little whimpers and moans and gasps were music to his ears and every one would make him go a little faster. A surge of magic washed over him and he shuddered, reaching down to grab Papyrus by the throat, applying a fair amount of pressure, "This was you- _fuck-!_ This was all you Pap. You- _sshit- shit!_ …You do this to me, e-every day.… I've been holding back for so long-!" 

 

Papyrus wasn’t sure exactly what he had done. He had certainly never done anything like this before! The most he had done towards anything like this was to experiment with his own body a little bit, this was something overwhelmingly new. He moaned long and loud as he rode his brother's cock, bouncing up and down to meet the almost violent, needy thrusts. It was beginning to feel better, and the friction hurt less and turned to a warmth that curled into his belly and to wherever Sans was touching. His neck tingled from where his brother was choking him, and where there was fear initially, a queer arousal replaced it and his head lolled to the side with an open-mouthed smile and a flaccid tongue hanging out the front. It was all so much but so good. 

 

Papyrus' silence was beginning to worry Sans until he remembered he was choking him, and released his hold, grinning devilishly at the gulp of air the other skeleton took in. He chuckled, eyes dim and lust-driven though one showed brightly with magic; he slowed his pace and took the time to ease himself in further, eating up the slow yell that Papyrus made as he did so. His dick brushed up against Papyrus' lower vertebrate as he was buried to the hilt inside his magic, he felt his brother's body moving and convulsing around him, the magic acting as a vacuum, constantly sucking on his member. 

 

Having gone a bit limp, Papyrus whined happily as his voice peeked out from screaming, his body deciding for him that being filled up like this, especially by someone he loved so much, was probably the greatest thing he had ever felt. 

 

Sans ate up the fucked senseless look on his brother's face, loving the drool slipping down his chin, and his glazed, distant eyes. He moved to make long, deep thrusts, moaning out Papyrus' name as he did so. "Oh you're so b-beautiful Pap, _nh-! Fuck-!_ " 

 

Papyrus covered his face with his hand, he wanted to say something in response but his ability to create conversational sentences was lost somewhere along the line. Sans grabbed his wrist and jerked his arm to the side, pinning it beside his head, "Don't you dare cover yourself," He warned through gritted teeth, "I want to see you." His voice was low and guttural and laced with domineering possessiveness. 

 

Harder and faster, he continued to bury himself in Papyrus, not knowing if any of this was real or some sick dream he was having. Papyrus felt so good; his magic was so lively and bright it felt amazing to be engulfed by it and to feel it radiating off of him as he was taken. Sans found the perfect angle where if he thrust upward just enough it would make his brother an insatiable mess 

 

"Mmmore, Sans! _Ah-ah-ah-aoh oh my... nnh!_ Yes, **ah-!** P-please, just like that, oh it feels _so good big brother!_ " Papyrus, for his lack of experience, was very lewd and knew what his body wanted, pulling on Sans' shirt as he cried out for more. He began grinding his hips down to meet each thrust, his magic pulsated in rhythm as well, applying a constantly shifting pressure to Sans' dick and making this just as invigorating for him. With his head slung back in delight, the older monster was laughing gutturally, low and maybe a bit wild; whenever he thought he was getting used to the sensation, something new happened, or Papyrus whined a fresh string of especially vulgar pleas that made his magic burn like lava. 

 

Papyrus stared up at his brother, completely dominating and possessive and overwhelmingly eager to give him a good time, he didn't think Sans could ever get like that, nor did he think he would be willing to put so much effort into something. He could not help entertaining the passing thought that maybe this was mostly for Sans' gain, and that brining him pleasure was merely a happenstance. However, the love in Sans' eyes, though clouded with lust and drive, was still there, and his willingness to do whatever Papyrus asked was endearing and made him feel like some sort of prince. He bathed in the praise Sans cooed when he wasn't talking so vulgarly; he would comfort him and compliment him, telling him how amazing he was and how much he wanted to do for him. The young monster happily listened to the kind words while he was being taken, smiling greedily as he did so. 

 

" _Oh fuck, Pap'-!_ " Sans' body jerked to a halt and he began shivering violently. Papyrus pulled himself up a bit, worried that something was wrong or he was hurt. However, it was obvious there was nothing to worry about as he watched Sans standing completely tense and flush, biting his lip and trying so hard not to move. 

 

It was all too much for him. Sans had done much wilder things before that didn't get him so close so quickly, but he was at his breaking point and he did not know how to proceed, and so did not move for fear of doing something Papyrus didn't want. His thoughts and words were stuck in his throat, so he was not saying so much as he was breathing heavily. 

 

"It's okay Sans," Papyrus whined, reaching out to lay a shaky hand on his brother's cheek, "I... I think I'm close t-too. I... want it." He smiled gently, making hazy eye contact with the other monster. 

 

Sans didn’t need much convincing. 

 

He leaned forward and grabbed Papyrus up, slinging his gangly legs around his waist and lifting him up and down on his cock, biting and kissing his brother's neck and shoulders. " _Ahh~_ Yes Sans, oh please, please-!" Papyrus cried, pushing down to gain as much contact as he could. They continued at a blistering pace, Sans bringing his partner down as hard as he could as fast as he could, moaning and cursing under his breath while he listened to Papyrus' needy exclamations. 

 

Sans' magic surged through him and he felt his repose break, "I'm-! **Fuck, Paa-ah ah!** " Pale blue magic burst from Sans' cock, drenching Papyrus' bones and filling the pocket of magic he was buried in with the warm sticky substance. He barely registered his brother crying out as the feeling of Sans releasing inside him was too much as he came as well. Papyrus continued to jerkily ride the other monster's member as he rode out his orgasm, happily cooing and moaning quiet praises and repeating his brother's name over and over. 

 

By the time his magic calmed enough for him to be fully cognoscente again, Sans finally felt a welcomed relief from the heat and need that had plagued him for a long time. Holding his brother, now limp and panting, in his arms was almost overwhelmingly rewarding and made him grin foolishly as he laid them both down. Papyrus looked to have been thoroughly claimed; Sans’ cum slid in globs off his narrow bones and glowed faintly in the dark of the room, Papyrus’ flaccid tongue and swollen middle were other soft sources of luminescence that shed light on a beautiful sight. 

 

Still coming down off his high, the younger monster was mumbling unintelligibly with a dopey grin on his face, obviously trying to rally his uncooperative limbs and languid muscles. Sans could occasionally pick out his name amongst the nonsense, but otherwise was content to listen as he propped himself up on his elbow to lazily stroke his brother’s chest. After a few minutes, Papyrus’ breathing evened out and he shut his eyes, curling into Sans’ chest and humming happily, “I love you, brother.” 

 

Guilt struck Sans again, now that his itch had been sated, he was reminded of his initial qualms and trepidations towards what he had just done. Panic began to rise in his chest and the pleasant post coital moment was ruined as he shot to his feet and briskly left the room, trying a little too hard to look casual. Once outside the door he teleported down the hall to the bathroom with a sharp _crack_ , he shut the door and turned to the sink, gripping either side of the basin until his fingers hurt. 

 

What had he done? He had let his dick act for him, that’s what he had done. Disgusting. 

 

He violently turned the cold water on and splashed himself in the face a few times, leaning over the sink as he feared he may vomit. The truth of what he had _forced_ on his baby brother was becoming too much, he was sure Papyrus would hate him once he came around, he would probably tell everyone what his big brother did to him, and he should, Sans was a monster for doing it. He clenched his teeth together and began to shake with anxiety, fearful tears prickling in his eyes in response to his guilt. 

 

There was a knock at the bathroom door, followed closely by a soft, sweet voice, “Sans? Are... are you alright?” 

 

Sans wanted to lie and tell him everything was fine, he was used to hiding his troubles from his brother, however, how could he hide what he had done? 

 

Another _crack_ resounded through the house and Sans stood in the living room, he didn’t dare look at the banister where he knew Papyrus would still be stood outside the bathroom door. He shrugged his hands into his shorts pockets as he headed towards the front door, wishing he had his hoodie, but not daring to risk heading back upstairs to retrieve it. “Sans!” Suddenly Papyrus was next to him, now dressed with a pair of shorts and his new sweater on, and grabbed his shirt hard enough to physically yank him away from the door as he was reaching for the handle. “Where are you going?” Papyrus wondered, voice fraught with worry, “Did I do something wrong?” He asked sadly. 

 

Sans teleported out of his brother’s grasp and stood a few feet away, he felt mad, furious at himself but also at Papyrus. How could the younger monster think he did anything wrong? How could he be so naïve and trusting to think that what just happened was alright, Sans couldn’t help but feel he had raised him wrong, sheltered him too much, not let him experience the world which led to blind trust such as that. 

 

“Of course not, Pap!” Sans spat, his magic lighting his eyes a fiery blue. Papyrus recoiled, looking scared, and Sans kicked himself again. “I did, I just...” He stopped, the words stuck in his throat, “I hurt you...” He mumbled, staring at the floor, guilt and anger clouding his vision. 

 

It was Papyrus’ turn to look offended, he reached out and took his brother’s arm, gently guiding him towards the couch, “You didn’t hurt me.” Papyrus said confused, “I don’t understand what’s wrong.” He sat down, becoming Sans to follow, which he did hesitantly, “It felt... Really nice!” The younger monster admitted, face flushing a light orange. 

 

Sans sighed and pressed himself into the couch, he couldn’t shake the overwhelming guilt he felt, his brother’s words helped ease his worries, but only a little, and he felt unworthy to be in the other’s presence. His mind was rushing with every bad situation that could happen from this point on, what people would say if they found out, how Papyrus would feel trying to have actual relationships after that, and how was he gonna move on now that he got a taste of what he’d always wanted... 

 

Papyrus shifted himself up against Sans, leaning down to rest his head on the shorter monster’s shoulder, Sans stiffened under the sudden contact, but relaxed as he let their combined scent lull him to ease. He carefully put his arm on Pap’s waist, dragging him over until he was practically on his lap, much like Mettaton had done earlier that day. He smirked at the small gasp he got in response, and the small playful slap he got as he let his hand drift lower to Papyrus’ rear. They sat like that for a few minutes, their breathing still a bit shaky from the preceding activities, their souls beating happily in-sync. 

 

“I promise I’m okay,” Papyrus mumbled into Sans’ neck after a while, “I promise you didn’t hurt me.” His small voice made Sans’ chest thrum in adoration, and he rubbed the younger monster’s back in reply, still not confident enough to say anything back. “I think... I think I’ve wanted it for a while too...” Papyrus whispered, catching the other off guard. 

 

A warmth curled in the pit of Sans’ stomach and his face heated up, but he forced himself to stay calm, tightening his hold on his brother, “You’re the only one I can imagine being with... like that. No one else is like us.” Papyrus explained, gently tracing Sans’ bones through his shirt, “And you’re the only one I love, brother.” Sans couldn’t see it, but Papyrus had a soft, loving smile on his face and a few happy tears just barely prickling along the bottom rim of his eyes. 

 

Sans pulled his brother even closer, completely hugging him against his chest, keeping his arms wrapped tightly around him. He buried his face in Papyrus’ sweater and tried not to get excited, tried not to outright cry hearing his baby brother say that; he was happy, for the first time in a while, he was happy and he felt on top of the world, “Damn bro...” Sans mumbled, shifting Papyrus so he could kiss him properly, using his thumb to gently wipe the tears off his brother’s face, “I love you too,” He said, meeting his partner’s eyes, both filled to the brim with affection, “Goddamn I love you!” Sans exclaimed with a laugh, lunging forward and scooping his brother up in his arms and kissing him again. 

 

They laughed together, idly kissing and recounting what had happened, before Papyrus spoke up, “I hate to take away from the moment but do you think I could go get cleaned up, I feel.... gross.” He asked, face flushing a dark orange as he averted his gaze. For a moment Sans was worried again, worried that the sex had left him feeling sick, however, he chuckled smugly when he looked down at his brother’s lap and saw his cum still stuck onto Papyrus’ femurs and leaking down from his pelvis. Papyrus noticed him staring and swatted at him again, “Hey don’t laugh! I didn't ask for this mess!” 

 

Sans chuckled and bit his lip, “Oh but you did, you were screaming it in fact.” He poked fun, sliding his hand up to rest on Papyrus’ filled middle, “I betcha like being stuffed full of your big brother’s c-” 

 

“ **SANS!** ” Papyrus screeched and covered his face, pulling away from Sans and beginning to march upstairs. 

 

“Aw you’re just gonna leave me with half a chub?” Sans giggled, watching the other’s march. 

 

Papyrus shot him a glare from the top of the stairs, “You still have a plate of cold spaghetti on your floor you need to clean up!” With that he trudged across the hallway and shut himself in the bathroom. Sans chuckled to himself, plopping back on the couch and letting the silence comfort him. He still felt guilty, but there was a happy buzz in his chest that made everything feel okay.

**Author's Note:**

> Thanks for reading!
> 
> I'd like to write more, shorter and probably kinkier fontcest fics now that I have this one done, I just felt I needed a precursor to pointless smut lol. Hope you enjoyed!
> 
> <3


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